1. Field of the Invention
The present invention relates to an alkoxylation catalyst and, more particularly, to an alkoxylation catalyst containing magnesium oxide as a major constituent.
2. Description of the Prior Art
An alkylene oxide adduct of an organic compound having one or more active hydrogen, such as an alcohol or phenol, is a valuable compound which is used in a variety of applications such as a solvent, a surfactant, and various intermediate chemical products. An alkoxylation reaction for producing such an alkylene oxide adduct is performed in the presence of an acid or alkali catalyst according to the following formula: ##STR1##
Examples of the conventional catalyst used in the above reaction are: a soluble, strong basic compound of an alkali metal such as lithium, sodium, potassium, rubidium, or cesium; a halide of a metal such as boron, tin, zinc, antimony, iron, nickel, or aluminum; an acid such as sulfuric acid or phosphoric acid; and a phosphate, a sulfate, a perchlorate, an oxalate, a carboxylate, and an acetate of a metal such as magnesium, zinc, or calcium.
These catalysts, however, have the following drawbacks. When the molar number of an alkylene oxide adduct is increased, an acid catalyst such as Lewis acid or a Friedel-Crafts catalyst causes a side reaction to produce a large amount of undesirable byproducts such as dioxane, dioxolane, or polyalkylene glycol. In addition, the acid catalyst has many disadvantages as an industrial catalyst. For example, the acid catalyst strongly corrodes metals. An adduct having a wide alkylene oxide adduct distribution can be obtained by a strong basic catalyst such as caustic potash or caustic soda. When soluble, basic compound catalysts of alkyl earth metals as described in U.S. Pat. Nos. 4,210,764, 4,223,164, 4,239,917, and 4,302,613 are used, the alkylene oxide adduct distribution can be narrower than that obtained with a conventional strong alkali catalyst, but is still wider than that obtained with the acid catalyst.